S,s&#39;-carbonyl-bis-dialkyldithiophosphate containing vulcanization accelerator

ABSTRACT

VULCANIZATION ACCELERATORS BASED ON S,S&#39;&#39;-CARBONYL-BISDIALKYLDITHIOPHOSPHATES AND A THIAZOLE ACCELERATOR WITH THE OPTIONAL INCLUSION OF THIURAMIC OR DITHIOCARBAMATE ACCELERATORS AND/OR THIOUREA, PROCESS OF VULCANZING TERPOLYMERS OF ETHYLENE AND PROPYLENE, I.E., EPDM RUBBERS, AND RESULTING PRODUCT.

US. Cl. 252-482 7 Claims ABSTRACT OF THE DISCLOSURE vulcanization accelerators based on S,S-carbonyl-bisdialkyldithiophosphates and a thiazole accelerator with the optional inclusion of thiuramic or dithiocarbamate accelerators and/or thiourea, process of vulcanizing terpolymers of ethylene and propylene, i.e., EPDM rubbers, and resulting product.

The present invention relates to a process for the vulcanization of terpolymers of ethylene and propylene, also known as EPDM rubbers, and more particularly to vulcanization accelerators for such a process.

As is well known, EPDM rubbers can be vulcanized with sulphur in the presence of an accelerator system which contains a conventional primary accelerator, e.g. one taken from the group of thiazole accelerators (see S. Bostrom, Kautschuk-Handbuch, vol. 4, Stuttgart 1961, pp. 300-307) and as additional accelerators those taken from the group of thiuramic and dithiocarbamate accelerators (see S. Bostrom, Kautschuk-Handbuch, Stuttgart, 1961, vol. 4, pp. 307-316) and optionally additional thioureas (see Technical Information Leaflet No. 20 of Farbenfabriken Bayer AG, published I an. 2, 1969, Order No. KA 4519). Without the addition of dithiocarbamate accelerators, the aforesaid accelerator systems only reach vulcanization rates which are too slow for technical purposes. Although the addition of dithiocarbamate accelerators, such as zinc dimethyldithiocarbamate or zinc diethyl dithiocarbamate increases the vulcanization rate, it entails the serious disadvantage that these accelerator systems in many cases cause the formation of unwanted surface deposits bloom on the surfaces of the vulcanizates (see Ullmanns Encyklop'adie der technischen Chemie, 3rd Edition, publishers Urban and Schwarzenberg, Munich and Berlin, 1957, vol, 9, p. 370).

In practice, the rate of vulcanization can only be increased to a very limited extent by increasing the amount of dithiocarbamate because larger amounts reduce the stability of the mixtures to such an extent that the process becomes unreliable (see Technical Informaion Leaflet No. 20 of Farbenfabriken Bayer AG, published Jan. 2, 1969, Order No. 4519).

The same applies to the addition of thioureas.

It has now been found that these disadvantages no longer occur in the vulcanization of ethylene propylene terpolymers in the presence of sulphur or sulphur donors and vulcanization accelerators if one uses as vulcanization accelerators S,S'-carbonyl-bis-dialkyl dithiophosphates of the general formula RO OR in which the radicals R denote the same or different straight chained or branched lower alkyl radicals each of which may be substituted by a lower alkoxy group,

with the addition of a conventional thiazole accelerator States Patent and, if desired, also a compound taken from the group of thiuramic or dithiocarbamate accelerators and/or optionally a thiourea. The lower alkyl radicals may have up to 6 carbon atoms and preferably have 1 to 4 carbon atoms. The lower alkoxy radicals mentioned above as substituents may have 1 to 4 and preferably have 1 to 3 C atoms. A lower alkyl radical R substituted with a lower alkoxy group may have a total of up to 10 carbon atoms.

The following are examples of radicals R in Formula I: Methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, tertiary butyl, n-pentyl, 3-methylbutyl, 2-rnethylbutyl, 2-pentyl, 3-pentyl, 3-methyl-2-butyl, 2- methyl-Z-butyl, 2,2-dimethylpropyl, n-hexyl, Z-hexyl, 3- hexyl, 4-methylpentyl, S-methylpentyl, Z-methylpentyl, 4- methyl-Z-pentyl, B-methyl-Z-pentyl, 3-methyl-3-pentyl, 2- methyl-Z-pentyl, 3,3-dimethylbutyl, 3,3-dimethyl-2-butyl, 2,2-dimethylbutyl, 2-methyl-3-pentyl, 2 ethylbutyl, 2- methyl-Z-pentyl, 2,3-dimethylbutyl, 2,3-dimethyl-2-butyl, Z-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-isoprop oxyethyl, 2-, ethoxypropyl, Z-ethoxypropyl, 2-propoxypropyl and 2-isopropoxypropyl.

The following are mentioned as examples of S,S'-carbonyl-bis-dialkyldithiophosphates which may be used in accordance with the invention:

S,S'-carbonyl-bis-dimethyl-dithiophosphate, S,S-carbonyl-bis-diethyl-dithiophosphate, S,S'-carbonyl-bis-di-n-propyl-dithiophosphate, S,S'-carbonyl-bis-di-isopropyl-dithiophosphate, S,S-carbonyl-bis-di-n-butyl-dithiophosphate, S,S'-carbonyl-bis-diisobutyl-dithiophosphate, S,S-carbonyl-bis-di-sec.-butyl-dithiophosphate, S,S-carbonyl-bis-di-tert.butyl-dithiophosphate, S,S'-carbonyl-bis-di-n-pentyl-dithiophosphate, S,S-carbonyl-bis-di-Z-methylbutyl-dithiophosphate, S,S'-carbonyl-bis-di-Z-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3-methyl-2-butyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methyl-Z-butyl-dithiophosphate, S,S'-carbonyl-bis-di-n-hexyl-dithiophosphate, S,S-carbonyl-bis-di-Z-hexyl-dithiophosphate, S,S-carbonyl-bis-di-3-hexyl-dithiophosphate, S,S'-carbonyl-bis-di-4-rnethyl-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methylpentyl-dithiophosphate, S,S-carbonyl-bis-di-2-methyl-2-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3,3-dimethyl-butyl-dithiophosphate, S,S'-carbonyl-bis-di-2,2-dimethylbutyl-dithiophosphate, S,S-carbonyl-bis-di-2-methyl-3-pentyl-dithiophosphate, S,S'carbonyl-bis-di-3-ethylbutyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methyl-pentyl-dithiophosphate, S,S-carbonyl-bis-di-2,3-dimethyl-butyl-dithiophosphate, S,S-carbonyl-bis-di-Z-methoxyethyl-dithiophosphate, S,S-carbonyl-bis-di-Z-ethoxyethyl-dithiophosphate, S,S'-carbonyl-bis-di-2-propoxyethyl-dithiophosphate, S,S-carbonyl-bis-di-2-isopropoxyethyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methoxypropyl-dithiophosphate, S,S'-carbonyl-bis-di-Z-ethoxypropyl-dithiophosphate, S,S'-carbonyl-bis-di-2-isopropoxypropyl-dithiophosphate, and S,S-carbonyl-bis-di-2-propoxypropyl-dithiophosphate.

'One may, of course, also use lS,S-carbonyl-bis-dialkyldithiophosphates of Formula I which have been obtained from alcoholic mixtures, e.g. isomeric mixtures such as a mixture of various isomeric butanols or pentanols or commercial alcoholic mixtures containing alcohols with different numbers of carbon atoms, these mixtures consequently having various radicals R (Formula I).

The vulcanization accelerators preferably used are S,S'-carbonyl-bis-di-n-butyl-dithiophosphate and S,S'-carbonyl-bis-isobutyl-dithiophosphate.

The accelerator systems according to the invention in addition contain an accelerator from the group of thiazole accelerators, for example Z-mercaptobenzothiazole, dibenzothiazyl disulphide or the Zinc salt of Z-mercaptobenzothiazole.

Additional accelerators taken from the group of thiuramio and dithiocarbamate accelerators may also be used, e.g. tetramethylthiuramic disulphide, tetraethylthiuramic disulphide, tetramethylthiuramic monosulphide, dimethyldiphenyl thiuramic disulphide and/or thioureas such as diphenyl thiourea, ethylene thiourea, N,N'-di methylthiourea, N,N-diethylthiourea, N,N'-dibutylthio urea and thiourea itself.

The individual components of the accelerator system may advantageously be used in the amounts indicated below (in parts by weight based on 100.0 parts by weight of EPDM rubber):

S,S' carbonyl bis dialkyl-dithiophosphate-approximately 0.1 to approximately 5.0

mercapto acceleratorapproximately 0.2 to approximately 2.0

thiuramic or dithiocarbamate accelerator-'0 to approximately 2.0

thiourea-O to approximately 2.0

The quantity of sulphur to be used is about 0.2 to about 3.5 parts by weight based on 100.0 parts by weight of EP'DM rubber, preferably 1.0 to 2.0 parts by Weight. Sulphur donors such as N,N'-dithio-bis-morpholine, dipentamethylene thiuramic tetrasulphide, N,N-dit.hio-bishexahydro-ZH-azepinone-(2) and Z-benzothiazyl-dithio- N-morpholide may also be used in quantities corresponding to the required amount of sulphur indicated.

The individual components of the accelerator system may be added to the EPDM rubbers or rubber mixtures before vulcanization either separately or in the form of a mixture or a preliminary mixture of rubber and accelerator (see Ullmanns Encyklop'adie der technischen Chemie, 3rd Edition, publishers Urban and Schwarzenberg, Munich and Berlin, 1957, Volume 9, page 364.

The EPDM rubbers may contain all the usual additives such as fillers, especially carbon blacks, mineral oils, plasticizers, tackifiers, accelerator activators, especially stearic acid, waxes, anti-oxidants, substances which protect against ozone, blowing agents, dyes or pigments.

vulcanization of EPDM rubbers is generally carried out at temperatures of between about 120 C, and about 300 C., using any of the usual vulcanization processes employed in industry such as press heating, heating with steam, hot air, salt baths, fluidized beds, ultrahigh frequency or steam pipes.

The compounds of the General Formula I may be prepared by reacting P S with the corresponding alcohol, neutralizing the resulting dithiophosphoric acid, preferably with an aqueous sodium or potassium hydroxide solution, and then phosgenating. The reaction may be explained by the following reaction scheme:

R-O s \H 1) NaOH P-S 2) 00012 O 2NaCl R-O S um] .20

In addition to the commercial pure alcohols, one may also use mixtures of alcohols ROH. Both isomeric mixtures, for example mixtures of n-propanol and isopropanol or of n-butanol and isobutanol or the isomeric mixture of various pentyl alcohols and mixtures of alcohols with different numbers of C atoms, e.g. a mixture of 50% by weight of n-butanol and 50% by Weight of n-pentanol may be used. One may, of course, also use commercial alcohol mixtures as Well as mixtures which contain numerous individual alcohols of diiferent chemical constitutions.

The reaction of phosphorus pentasulphide with alcohol or alcohol mixtures is carried out under normal or elevated pressure in a temperature range of 10 C. to C., preferably at 30 C. to 50 C. and normal pressure. The reactants are advantageously put into the process in equimolar quantities although an excess or subequivalent amount of phosphorus pentasulphide may, of course, be used. Furthermore, phosphorus pentasulphide may be put into the reaction with the corresponding alcohol or alcohol mixture diluted with an inert organic solvent such as cyclohexane, benzene, toluene, xylene or diethylether, diisopropylether, tetrahydrofuran or dioxane. Alternatively, phosphorus pentasulphide may, of course, be suspended in one of the above-mentioned solvents and reacted in this form with the corresponding alcohol or alcohol mixture. It will generally be preferable to introduce the dry phosphorus pentasulphide into the reaction vessel and slowly add the undiluted alcohol or alcohol mixture. The dialkyl or dialkoxyethyldithiophosphoric acids obtained in this way are liquid compounds. For subsequent reactions, neutralization of the corresponding dithiophosphoric acid with ammonia or an amine such as triethylamine or pyridine may be carried out in another solvent such as diethylether, diisopropylether, dioxane, tetrahydrofuran, benzene, toluene or xylene but preferably, neutralization of dithiophosphoric acid is carried out in water, using an amine such as triethylamine or ammonia but more simply still with aqueous alkali metal hydroxide solutions such as sodium hydroxide or potassium hydroxide solution at room temperature. The salt solutions prepared in this way can now be directly converted into the corresponding S,S'-carbonylbis-dialkylor S,S'-carbony1- bis dialkoxyethyl-dithiophosphates by means of phosgene. The phosgenation reaction may be carried out in a temperature range of -20 C. to 100 C., preferably between 5 C. and 10 C., and the reactants may be used in stoichiometric quantity or phosgene may be used in excess. If the reaction is carried out in an aqueous phase, an inert organic solvent such as cyclohexane, benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, ethylene chloride, diethylether or diisopropylether may be added.

As will be seen from the following examples, the vulcanization accelerators according to the invention are distinguished by their high resistance to premature vulcanization. They achieve a high vulcanization rate and excellent mechanical properties in the vulcanizates, in particular a low compression set (in accordance with DIN 53 517) and high tension values, tear resistances, elasticity and hardness. In particular, they do not cause blooming or matting of the surface of the vulcanizates. The compounds which have more than 3 carbon atoms in the alkyl radicals are practically odourless and do not impart an odour to the vulcanizates.

The vulcanization process according to the invention Will be explained in the following examples. The test methods used are summarized in Table 1.

TABLE 1 Modulus (3) F Tear resistance (kg. wt./cm. DIN 53 504, standard ring RI.

(4) D Elongation at break (percent), DIN 53 540, Sheet 1, standard ring RI.

(5) H Hardness (Shore A), DIN 53 505,

region A, 4 mm. flaps.

As can be seen from the above data, especially the increase in modulus with the heating time, S,S'-carbonylbis-dialkyldithiophosphates (mixtures Nos. 1 to are A furnace black which improves the extrudability of the mixture (FEF carbon black, Corax Parts by weight superior in their resistance to scorching and as regards A 1 h-t f-Tzfg-g-igg blooming. Whilst zinc diethyldithiocarbamate (mixture f i g mmera g p No. 6) causes severe blooming, the vulcaniz s obtamed s z acid with 5,3 carbon l-bis-dialkyldithiophosphat s remam Sulphur 15 clear on the surface. In addition S,S- r o y z mercaptobenzothiazole 5 tyl dithio hosphat (m ur 0- has advantages i Tetramethyl-thiuramic monosulphide 0.4 regards. the modulus level compression set of e The following accelerators were then mixed on a mill: vulcamzates. When compared wlth mixture No. 7 (WhlCh Mixture No n 0 iazo an tetrameth ls coptalns 2 f fiif g i also gg 1: S,S'-carbonyl-b1s-d1methyldithlophosphate 1.2 t j P if d t f S b 1 2; S,S'-carbonyl-bis-diethyl dithiophosphate 1.2 not g ve riseto oormng, t e a van ages 0 -car ony 3: carbonyl bis di n propyl dithiophos bis-dralkyl-dithiophosphates as regards vulcaniza i n r phate. 1.2 e and the mechanical properties obtained, especially the 4: carbonyl bis di isopropyl dithiophos compression set, become very clear. phate 1 2 5: S,S carbonyl-bis-di-(2 methoxyethyl)-di- EXAMPLE 2 thiophosphate 1.2 6: SS carbonyl-bis-di-n-butyl dithiophos- The following EPDM rubber m1xture was prepared 1n phate 12 an internal mixer in the usual manner: Zinc diethyl dithiocarbamate L2 Parts y welght 8: Without additive A raplifly Vulcamzmg type of E PDM contammg Stepwise heating at 120 C., 150 C. and 170 C. was ethylldene nol'bomelle as dlme Component carried out with the above mixtures and the following (Keltan 512) 100.0 data were obtained:

TABLE 3 Mixture Number 1 2 3 4 FDM,M,HEFDM,M,HEFDM,M,HEFDM,M,HE

Bminutesat 120C 10 250 48 10 190 33 48 10 230 3 33 49 5 190 33 49 10minutesat 120C. 10 290 48 10 220 3 34 48 10 170 35 49 10 230 3-.'.- 35 50 15 minutes at 120C 10 552 48 10 310 4 3 38 49 10 400 49 10 330 4 3 39 49 20 minutes at 120 C- 10 550 49 10 550 7 8 45 49 20 580 51 10 350 7 8 45 49 30minutes at 120C.-- 690 51 730 16 22 45 51 30 750 51 45 720 16 22 51 45 minutes at 120C--- 113 780 51 120 680 34 553 52 51 140 680 52 105 600 34 54 62 51 mir1utesat120C 140 720 51 125 530 45 70 65 51 145 570 53 120 480 49 75 55 52 75minuteSat120C 140 530 52 130 490 54 82 57 53 145 510 53 115 420 55 83 67 52 90 minutes at 120C. 145 540 53 140 420 58 100 53 140 420 54 120 350 Bminutes at 150 0 25 540 50 35 640 14 19 58 5o 40 610 51 25 600 IOminutes at 150C. 140 750 51 145 660 42 55 54 51 150 650 53 130 580 15minutesat150O 150 540 51 135 440 51 92 68 53 150 480 54 130 420 20 minutes at 150C--- 150 550 51 145 400 70 105 69 53 145 410 54 135 380 30 minutes at 150c 155 490 53 140 340 79 122 70 54 145 370 54 130 330 45 minutes at 150C.-. 155 420 54 145 310 88 137 72 54 140 300 55 130 290 60minutesat150C 150 390 54 135 280 54 130 250 55 135 270 75minutes at150C 155 390 52 140 290 54 140 280 55 125 250 90 minutes at 150C- 155 390 54 140 280 54 145 290 55 135 280 Emlnutes at 170 0-- 160 520 51 150 450 61 94 67 52 155 460 54 140 430 10 minutes at 170 C- 155 450 52 155 350 128 70 53 150 340 54 140 330 15 minutes at 170 150 470 50 98 55 52 145 330 82 131 70 53 135 300 54 134 300 Scorch time at 120 0. (min.).. 38 35. 5 Maximum modulus at 200% elongation at 150 C. (llmitingv kg. wt./cm 72 97 Blooming None None Compression set (percent) 5minutes at 120C 10 170 37 33 48 5 180 4 33 50 10 minutes at 120 0- 10 450 8 7 45 37 48 30 650 12 29 45. 50 15 minutes at 120 0. 35 550 61 22 53 44 48 35 720 30 48 54 50 20 minutes at 120 0. 770 25 39 58 51 50 510 48 53 58 51 30 minutes at 0. 140 750 35 56 52 60 51 120 470 54 81 51 51 45 minutes at 120 c. 155 590 43 75 55 55 53 135 450 52 94 53 52 60 minutes at 129 0 155 530 55 85 56 57 53 140 410 69 97 65 53 75 minutes at 120C- 155 470 53 95 68 59 54 135 390 72 89 65 54 90 minutes at 120 C. 150 410 72 108 69 70 54 350 74 101 55 54 fiminutes at 150 0.- 130 800 30 49 59 54 51 110 510 23 34 53 51 10 minutes at 150 C- 160 570 54 85 55 55 52 130 550 53 80 55 51 15 minutes at 150 C--- 150 420 65 101 58 58 54 430 68 87 57 53 20 minutes at 150 C.-- 155 400 74 114 58 59 54 135 420 74 94 68 54 30 minutes at 150 0. 145 350 82 129 70 70 54 350 80 110 59 53 45 minutes at 150 C 310 90 143 70 70 54 140 320 83 123 59 54 60minutesat150 C 140 280 94 71 71 55 145 270 87 70 54 75 minutes at C 140 280 95 71 71 54 130 250 89 70 54 90 minutes at 150 C- 150 300 94 148 72 72 54 130 270 90 70 54 Gminutes at 170 0.. 150 440 68 107 57 57 52 140 410 59 102 58 51 10 minutes at 170 0. 350 84 135 59 59 54 135 340 79 125 58 53 15minutes at 150 330 85 137 59 59 54 135 330 79 59 54 Scorch time at 120 C.(min 19.5 14 Maximum modulus at 200% elongation at 150 C. (limiting value 907150 0., kg. wt./em. 94 96 90 87 looming None None Severe None Compression set (percent;

2 h./70 C 8.0 8.0 10.2 11.3 70 l1./100 C 50.2 49.2 55.3 57.8

9 EXAMPLE 3 The following mixture was prepared in an internal mixer in the usual manner:

Parts by weight The following compounds were synthesized in analogous manner:

S,S'-carbonyl-bis-di-methyl-dithiophosphate; 12 1.5438 C H P S (311.4): Calc. (percent): C, 19.3; H, 3.39.

A slowly vulcanizing type of EPDM containing di- 5 Found (percent). C, H, 45

cyclopentadmne as diene component (Kel S,S'-carbonyl-bis-diethyl-dithiophosphate; n 1.5249 520) 100-0 C H O P- S 395.5 Calc. (percent): 0, 27.1; H, 5.1. A furnace black which 1mproves the extrudability Found (percent); C 26.4. H 51 of the mixture (Corax carbon black) S S'-carbon l-bis-di-iso ro l-dithio ho hate' P 82- An aliphatic mineral oil (Ingraplast NS) 20.0 y P W p Sp Zmc C13H28O5P2S4 Steam: ac1d S,S'-Ca1bonyl-bis-di-n-propyl-dithiophosphate; 71 1.5239 Sulphur 0 51 0 155, 454.5 Calc. (percent): 0, 34.4; H, 5.2. b Found (percent): 0, 34.0; H, 5.5 T?trameth3(1 thmramlc monosulphlde I5 S,S'-ca'r'bonyl-bis-di-(2 methoxyethyl)-dif hiophosphate; D1phenylth1ourea n 1.5371

The accelerators were then mixed on a mill (parts by 15 55 4 Calc- (P weight based on 100.0 parts by weight of rubber): Found (P Q= Mixture No 20 S,S'carbony1-b1s-di-n-pentyl-dithiophosphate; n 1.5173 1: S, S'-ca rbonyl-bis-di-n-butyldithiophosphate 1.2 rlcenoz 44's; 2: Zmc dlethyl dlthlocarbamate S,S'-Calbonyl-bis-di-n-hexyl-dithiophosphate; n 1,4961 Stepwise vulcanization was carried out at 120 C. and C H O P 'S (622.9): Calc. (percent): C, 48.2; H, 8.4. 150 C. with the above mixtures and the following data: Found (percent): C, 49.2; H, 9.3

TABLE 4 Mixture Number FD200300HEFD200300HE 51515515555125" 0 15 225 4 55 4s 15 205 5 57 47 10minutesat120 o 15 715 9 15 45 4s 25 555 24 55 45 4s 20minutes at 125 0 55 855 15 25 52 45 75 755 50 42 4s 4s 50 minutes at 125 0 115 555 25 5s 55 45 100 750 55 4s 55 4s 45 minutes at 120C 155 555 51 50 59 48 155 750 45 55 55 49 55 minutes at 125 0 155 555 42 555 51 50 155 555 44 55 59 55 75 minutes at 125 0 175 515 45 75 55 51 155 555 45 57 51 5o 95 minutes at 120 0 155 555 55 77 54 51 155 520 49 75 52 55 Eminutes at 155 c 124 595 24 55 125 755 54 49 5s 4s 15 minutes at 155 0. 175 725 59 52 55 45 150 575 42 57 59 49 15 minutes at 150 0 175 590 49 77 52 49 155 515 47 54 55 20 minutes at 155 0 150 515 57 55 51 155 555 51 52 55 155 520 55 52 51 155 525 55 55 52 51 155 555 77 121 55 51 155 455 72 55 51 155 555 75 127 59 55 155 415 75 111 55 52 155 520 55 157 59 55 155 595 79 57 52 95 minutes at 150 0 155 545 57 70 55 555 81 55 52 Scorch time at 120 0.

(min) 23 12 Maximum modulus at 200% elongation at 150 C. (limiting value 957150 0. kg. wt./ cmfl) 81 Blooming None Severe EXAMPLE 4 S,S'-carbonyl-bis-di-isohutyl-dithiophosphate; 71 1.5203 1117 g. (15.5 mol) of n-butanol are added dropwise i gffg z g g'7 g g g 40'0; to 860 g. (3.87 mol) of phosphorus pentasulphide at 20 p C. (cooling with water) with stirring. Stirring is them When usinganalcoholic mixture of 50 percent b weight continued at 50 C. until the evolution of hydrogen sul- 55 of n-butanol and 50 percent by weight of isobutanol, a phide has ceased. The reaction mixture is cooled to room product which has the following data is obtained: temperature, degasified under vacuum and filtered. 1775 C H O P S 36 5 2 4 (510.7). Calc. (percent): C, 40.0; H, 7.1. gieogbttiblugldithiophosphorlc ac1d (97% of the theory) Found (percent) C, 39.8; H, 72. "D20 1.5258

820 g. (3.1 mol) of sodium-di-n-butyl dithiophosphate 60 When an alcoholic mixture of 50% by weight of nwhich can be prepared by treating dibutyldithiophosphoric butanol and 50 percent by weight of n-pentanol is used, acid with aqueous sodium hydroxide solution in the usual a reaction product which has the following overall commanner are reacted with 153.5 g. (1.55 mol) of phosgene position is obtained: in 1.6 l. of water at '5 C. to 0 C. Stirring is continued for 2 hours at 0 C. and the reaction mixture is then made 65 iggfi z i gg'j k 3 2" g gi g 'g slightly alkaline and extracted by shaking it 3 times with What w q I methylene chloride. The combined methylene chloride 1 A v i i l I t n f solutions are washed with water, dried over sodium sul- 3 era i consls mg 689m 13 y o phate and evaporated under vacuum. 803 g. of a pale ac p 0 e ormua yellow oil, amounting to 100% of the theory (based on 70 R0 8 3 OR the amount of sodium dibutyldithiophosphate put into the H H reaction) of S,S-carbonyl-bis-di-n-butyldithiophosphate are obtained; n 1.5265. 30 OR C17H35'05P2S4 (510.7): Calc. (percent): C, 40.0; H, 7.1;

O, 15.7; P, 12.1; 'S, 25.1. Found (percent): C, 39.8; 75 wherein each R is alkyl having from 1 to 6 carbon H, 7.2; O, 16.5; P, 12.1; S, 24.5.

atoms or alkoxyalkyl having from 1 to 4 carbon 1 1 atoms in the alkoxy moiety and 1 to 6 carbon atoms in the alkyl moiety and, for each 0.1 to 5.0 parts by weight of (a), from approximately 0.2 to approximately 2.0 parts by weight of (b) a thiazole accelerator.

2. The vulcanization accelerator of claim 1 wherein said (b) is Z-mercaptobenzothiazole, dibenzothiazyl disulphide or a zinc salt of Z-mercaptobenzothiazole.

3. The vulcanization accelerator of claim 1 containing for each 0.1 to 5.0 parts by weight of (a), up to approximately 2.0 parts by weight of (c) tetramethylthiuramic disulphide, tetraethylthiuramic disulphide, tetramethylthiuramic monosulphide or dimethyldiphenylthiuramic disulphide.

4. The vulcanization accelerator of claim 3 containing for each 0.1 to 5.0 parts by Weight of (a), up to approximately 2.0 parts by weight of (d) a thiourea.

5. The vulcanization accelerator of claim 1 comprising S,S'-carbonyl-bis-di-n-butyl dithiophosphate and 2-mercaptobenzothiazole.

6. The vulcanization accelerator of claim 5 containing for each 0.1 to 5.0 parts by weight of (a), up to approxi- References Cited UNITED STATES PATENTS 2,841,520 7/1958 Willard et al 26O--928 3,388,193 6/1968 Yamaguchi et al 260928 3,435,010 3/1969 Starer et a1. 260-79.5 C 3,489,803 1/ 1970 Maier 260-928 3,537,998 11/1970 Lowe 252400 3,544,465 12/1970 Braid 252400 LEON D. ROSDOL, Primary Examiner I. GLUCK, Assistant Examiner:

US. Cl. X.R. 

